Our histopathologic studies performed during the previous grant period have characterized the histopathological and mineral composition in three groups of stone formers: common idiopathic calcium oxalate stone formers, patients with stones due to intestinal bypass surgery for obesity and brushite stone formers (as well as non-stone formers) to test the hypothesis that Randall's plaque, calcium phosphate deposits in kidneys of patients with calcium renal stones, arise in unique anatomical regions of the kidney, their formation conditioned by specific stone-forming pathophysiologies. We were amazed at the finding, in that, each group of stone formers had a different and unique histopathologic pattern of crystal desposition while all intraparenchymal and interstitial sites of crystalline material were hydroxyapatite, yet another surprise. Because we were so highly successful in the last funding period in identifying a clear set of surgical/ morphological/metabolic characteristics in these three different groups of human stone formers (CaOx, intestinal bypass for obesity and brushite) and will extend these analyses to new groups of stone formers: apatite (including RTAs) stone formers, primary hyperparathyroidism with kidney stones, ileostomy with kidney stones, cystine stone formers, uric acid stones, bariatric patients with stones and CaOx stone formers with high urine pH (>pH 6.3) using histopathology,mu CT, and mu FTIR. In addition, we will seek to test a new set of hypotheses concerning the mechanisms of stone formation. First, we will test the hypothesis that the progression of HA accumulation occurs along a specific segment of the loops of Henle, the thin descending limb. Second, the mechanism of crystal particle formation and coalescence in the common CaOx patients will be determined by quantitative TEM and tetracycline studies. Third, test the hypothesis that there are candidate proteins that either promote or inhibit crystal nucleation and growth within the papillary interstitium or tubular lumens. This will be done using TEM immunohistochemical analysis to define the interaction of osteopontin, prothrombin fragment 1,fetuin-A and bikunin on interstitial and the plaque-stone interface. Fourth, we will use RT-PCR techniques to detect transcripts for the presence of osteoblast-like activity. Lastly, we will examine the idea that a loss of fluid pH control in the inner medullary collecting ducts due to SWL injury may result in an alkalization of the bulk urine and, therefore, give insights into the mechanisms of stone formation in brushite stone disease.